Soil-release behaviour of polyester fabrics after chemical modification with polyethylene glycol

The ease of cleaning the fibers depends, among other characteristics, on their hydrophilicity. Hydrophilic fibers are easy-wash materials but hydrophobic fibers are difficult to clean due to their higher water-repellent surfaces. This type of surfaces, like polyester (PET), produce an accumulation of electrostatic charges that adsorbs and retain dirt. Thus, the polyester soil-release properties can be increased by finishing processes that improve fiber hydrophilicity [1, 2]. In present study, PET fabric modification was described by using polyethylene glycol (PEG) and dimetilol dihidroxy ethylene urea chemically modified resin. Briefly, the modification process was carried out in two steps, one to hydrolyse the polyester and create hydroxyl and carboxylic acid groups on surface and the other to crosslink the PEG chains. The resulting materials were characterized by contact angle, DSC and FTIR- ATR methods. Additionally, the soil release behavior and mechanical properties of modified PET were evaluated. For the best process conditions, the resulted PET presented 0º contact angle, stain release grade of 5 and acceptable mechanical performance.Programme - COMPETE and by national funds through FCT – Foundation for Science and Technology within the scope of the project POCI-01-0145-FEDER-007136.info:eu-repo/semantics/publishedVersio

Tribological properties of the directionally oriented warp knit GFRP composites

Recently, directionally oriented warp knit structures have gained prominence as reinforcements in composite materials due to their superior isotropic behaviour compared to other types of textile reinforcements. In the present study, composites prepared from four types of directionally oriented warp knit glass preforms with three different thermoset resins have been considered for the tribological characterisation. The tribological tests have been conducted on a reciprocating sliding test rig with ball-on-plate configuration. The tests were conducted in dry (unlubricated) and wet (aqueous) conditions at a fixed applied load (100 N) by varying the sliding distance. E-glass warp knitted preforms were used for the study including biaxial, biaxial non-woven, triaxial and quadraxial fabrics. The matrices were three different thermoset resins namely polyester, vinyl ester and epoxy resin. 13 14 15 16 17 18 19 The main aim of the study was to identify a composite having the best tribological performance, with regard to types of preform and matrix resin. Moreover, the results obtained from the tests have been used to develop a wastage map for these composites, as a function of sliding distance and type of preform in order to have a clear understanding of the tribological process.Fundação para a Ciência e a Tecnologia (FCT

Finite element analysis of Carbon composite sandwich material with agglomerated Cork core

AbstractComposite sandwich structures were developed for the hydrofoil sail boat hull using biaxial carbon fabric/epoxy composite facing and agglomerated cork core. These ultra-light weight structures were tested through four point bending tests to characterize their flexural behavior. The material exhibited an initial linear elastic behavior followed by non-linear elastic-plastic behavior. Finite element analysis of the sandwich beams was performed to analyze the flexural behavior of the structure. It was found that the transition from linear elastic to non-linear elastic-plastic behavior is the result of compressive yielding of core material which leads to indentation in the beam. This also causes initiation of failure in the core. A shift in the centroid axis of the beam towards the tensile face was also observed. The sandwich structures made of cross-linked PVC and PMI foam cores were also analyzed for comparison. Further, a parametric study on the effect of areal density and ply angle of the facing fabric and core thickness were performed using finite element method. The parametric study revealed that the transition from linear to non-linear trend is caused by different mechanisms with the change in the mentioned parameters

Tribological behaviour of multilayered textile composites: the effect of reciprocating sliding frequency

Textile composites have been used for various applications because of their enhanced strength/weight ratio and versatile properties compared to other materials such asmetals. Many studies have investigated the tribological behaviour of textilecomposites, but none have focused onthe tribological characterization of 3D multilayeredwoven reinforced textile composites. Five types of 3-plywoven interlocked structures with varying interlacements were used as reinforcement for the nylon fibre/polyester resin composites for the present study. The influence of the textile structure interlacement on the tribological properties of the composite material (in terms ofwear volume)was investigated in thiswork. Further, special attention was given to understand the effect of sliding frequency on the tribological behaviour and driving wear mechanisms. The tests were conducted on a new class of reciprocating sliding wear tester, in dry (unlubricated) conditions, under a fixed applied load of 20N by varying the frequency of oscillating motion (0.5≤f≤8 Hz). In addition, testswere also conducted, at a constant frequency of 4Hz and as a function of several loads (5Nto 40 N). Fromthese tests, a 3-plywoven reinforced composite with the best tribological performance as a function of frequency and load was identified. It was observed that the type of woven structure had an influence on the tribological properties. Therefore, the selection of a textile composite should be based on the load and frequency at the service condition. The wear mechanisms involved in the tribological process were also analysedThe authors would like to express their gratitude for financial support provided by FCT, Portugal, through an individual project (SFRH/BPD/20344/2004), and an Asia Link program between the University of Minho, Portugal, and IIT Delhi, India, sponsored by the European Union. Thanks also to Mr. Sérgio Carvalho, who assisted with experimental work in the Tribology Lab at University of Minho